The field of the disclosure relates generally to propellant transfer and, more particularly, to methods and systems for estimating propellant transfer in an ion propulsion system.
Some known satellite propulsion systems include two storage tanks separated by a high pressure latch valve. Gas propellant for the satellite's propulsion system is stored in the storage tanks. When propellant is transferred from one storage tank to another, the amount of gas transferred between tanks and the amount of propellant remaining in each tank is estimated. Some known systems use a propellant P-V-T Gauging Tool to estimate the transfer of gas propellant. The latest pressure and temperature sensor reading for each tank are used to determine the volume of propellant in each tank and to retrieve the corresponding fluid density from a properties table. The mass of the gas propellant is calculated based on the calculated volume and retrieved density. During transfer of the gas, these known systems do not update the pressure and temperature profile. Rather, the measurements and calculations described above are performed before the transfer begins, the time to transfer the desired amount of gas propellant is calculated based on the initial estimations, and the calculations are not updated or repeated until after the transfer is completed. During transfer of the gas propellant, temperature and pressure typically change, resulting in changes in the characteristics of the gas propellant and variations in the flow rate of the gas. These changes may lead to inaccuracies in the estimation of the amount of gas transferred.